Methods of preparing 7XXX aluminum alloys for adhesive bonding, and products relating to the same

Abstract

Methods of preparing 7xxx aluminum alloy products for adhesive bonding are disclosed. Generally, the methods include chemical and/or mechanically preparing a 7xxx aluminum alloy product to reduce the amount of magnesium oxides while maintaining any copper-containing intermetallic particles located proximal the surface of the 7xxx aluminum alloy product. After preparation, a functionalized layer may be produced thereon for adhesive bonding.

What is claimed is: 
     
       1. A method comprising:
 (a) receiving a 7xxx aluminum alloy sheet, wherein the 7xxx aluminum alloy sheet comprises a surface oxide layer;
 (i) wherein the surface oxide layer comprises an as-received thickness; 
 (ii) wherein the surface oxide layer comprises magnesium oxides and aluminum oxides; 
 (iii) wherein the 7xxx aluminum alloy sheet comprises copper-bearing intermetallic particles at least proximal the surface oxide layer; 
 
 (b) reducing the as-received thickness of the surface oxide layer to a preparation thickness, wherein the reducing comprises maintaining a volume fraction of the copper-bearing intermetallic particles proximal the surface oxide layer; 
 (c) after the reducing step (b), creating a functional layer bonded to the 7xxx aluminum alloy sheet. 
 
     
     
       2. The method of  claim 1 , wherein the copper-bearing intermetallic particles comprise Al 7 Cu 2 Fe particles. 
     
     
       3. The method of  claim 1 , wherein the reducing step (b) comprises:
 contacting the surface oxide layer with a preparation solution for a time sufficient to reduce the as-received thickness to the preparation thickness while maintaining the volume fraction of the copper-bearing intermetallic particles proximal the surface oxide layer. 
 
     
     
       4. The method of  claim 3 , wherein the preparation solution is alkaline. 
     
     
       5. The method of  claim 4 , wherein the preparation solution comprises a pH of not greater than 10. 
     
     
       6. The method of  claim 4 , wherein the contacting step occurs for at least 20 seconds. 
     
     
       7. The method of  claim 4 , wherein the contacting step occurs for at least 60 seconds. 
     
     
       8. The method of  claim 4 , wherein the contacting step occurs for at least 90 seconds. 
     
     
       9. The method of  claim 4 , wherein the preparation solution comprises a preparation temperature during the contacting step, wherein the preparation temperature is from 100-150° F. 
     
     
       10. The method of  claim 3 , wherein the preparation solution is acidic. 
     
     
       11. The method of  claim 10 , wherein the preparation solution comprises a pH of not greater than 3. 
     
     
       12. The method of  claim 10 , wherein the preparation solution is nitric acid. 
     
     
       13. The method of  claim 10 , wherein the preparation solution comprises a preparation temperature during the contacting step, wherein the preparation temperature is from 70-90° F. 
     
     
       14. The method of  claim 3 , wherein the reducing step (b comprises contacting the surface oxide layer with a preparation solution for a time sufficient to reduce the as-received thickness to the preparation thickness and in the absence of substantial de-alloying of the copper-bearing intermetallic particles proximal the surface oxide layer. 
     
     
       15. The method of  claim 1 , wherein the reducing step comprises mechanical preparation. 
     
     
       16. The method of  claim 15 , wherein the mechanical preparation comprises media blasting. 
     
     
       17. The method of  claim 15 , wherein the mechanical preparation comprises at least one of grit blasting, machining and sanding. 
     
     
       18. The method of  claim 1 , wherein, after the reducing step, the preparation thickness of the surface oxide layer is not greater than 20 nm. 
     
     
       19. The method of  claim 1 , wherein, due to the reducing step (b), the surface oxide layer comprises not greater than 10 at. % magnesium oxides. 
     
     
       20. The method of  claim 1 , wherein the 7xxx aluminum alloy product comprises 2-12 wt. % Zn, 1-3 wt. % Mg, and 1-3 wt. % Cu.